The Chronicles of Nautilus from Spring 2018 Shorelines Monterey Bay Aquarium Member Magazine

MONTEREY BAY AQUARIUM SHORELINES

The Chronicles of Nautilus

Even though the chambered nautilus is an ancient species, there's still so much biologists don't know about hatching and raising the young of this most primitive of cephalopods.

We're thrilled to be part of an exclusive group that has accomplished this feat. We still have a lot to learn and a long way to go before we can reliably propagate chambered nautilus.

Aquarist Ellen Umeda's job is to discover what works (and doesn't) to hatch and raise one of the most challenging species kept at any aquarium. Ellen's entering unknown territory, but is delighted that along the way she gets to explore the mysterious world of the long-lived chambered nautilus.

We spoke to Ellen exclusively for Shorelines online about the chambered nautilus, our progress in breeding them, and about cephalopods in general.

Congratulations on the chambered nautilus hatchlings! What does this achievement mean to you as a biologist?
Thank you! I'm excited to have this unique opportunity to work with an animal that rarely hatches in an aquarium. It will certainly be a challenging journey, but there is still so much to learn and explore!

A chambered nautilus hatchling begins to emerge from its egg in a behind-the-scenes nursery. It's one of hundreds laid by adults in our Tentacles special exhibition.

Tell us more about your R&D with chambered nautilus eggs and hatchlings, and what you hope to accomplish.
I've been fortunate to talk to staff at other aquariums about their experiences with chambered nautilus hatchlings—specifically what worked and didn't work. Historically, raising hatchlings to adulthood has proved challenging. Very few hatchlings survive to a year, which is a very young age for an animal that reaches maturity around five years. I hope to use scientific research about the physiology and ecology of wild chambered nautilus and apply it to raising hatchlings in an aquarium.

For example, chambered nautilus live at deeper depths, below 328 feet (100 meters). The higher water pressure at these depths potentially plays an important role in its ability to properly form new chambers in its shell as it grows. These chambers help the nautilus maintain buoyancy in the water column. I've been working with our Curator of Collections, Joe Welsh, to use pressure chambers for housing eggs and hatchlings. But many more factors likely play a role in successful nautilus culture, and figuring out these factors remains a challenge.

Walk us through the lifecycle of a chambered nautilus—what we know and don't know.
No one has been able to document the entire life cycle of a chambered nautilus in the wild. In fact, no one has seen an egg, and young hatchlings are rarely seen. From what we've seen at the Aquarium, adult nautilus mate and females lay eggs about one inch in size throughout the exhibit, tucked between the corals or under ledges. Nautilus eggs have an unusual, rigid shape consisting of a teardrop structure inside containing the developing hatchling, and an outer layer with small holes at the top to allow for water circulation. Gestation varies depending on water temperature, but can be as short as nine months for warmer temperatures and as long as 15 months for colder temperatures.

Once ready, the developing hatchling emerges completely from the egg. Nautilus hatchlings do not require any parental care and know how to swim and feed as soon as they hatch. As the hatchlings grow, new chambers form in their shells—hence the name chambered nautilus. It is estimated that chambered nautilus reach sexual maturity around five years, at which point the cycle starts again and the next generation begins.

We regularly measure the baby chambered nautilus to document their rate of growth.

When during development do they grow their chambered shell?
They begin growing their chambered shell while in the egg. In fact, as the shell grows bigger and no longer fits in the egg, the egg splits open and exposes the top of the shell. The developing chambered nautilus will continue to grow for several months with its shell sticking out of the egg and eventually hatches out as a miniature, one-inch version of an adult nautilus.

The chambered nautilus has changed little over the last 150 million years. Why is that?
Despite the chambered nautilus' primitive eyes and body structure, these features enabling survival 150 million years ago are still suitable for survival today.

What's it like to work with the adults of this species?
It's awesome to work with such an unusual species! The adults tend to sit in one place for a majority of the day. But don't let this fool you; they swim around while you clean the exhibit in the morning or while you feed them. Occasionally, one will get curious and attach to your cleaning tools or hand with its tentacles. Unlike other cephalopods, nautiluses can have up to 90 tentacles! Their tentacles don't have suckers like cuttlefishes and octopuses. Instead, their tentacles have little grooves that allow them to grab onto food and other surfaces.

Baby nautilus are kept in low-light conditions, similar to the deep water they inhabit in the wild. They are hand fed by Ellen and other aquarists.

How is caring for cephalopods different than for other marine species?
Cephalopods are very sensitive, high-maintenance animals. They eat a lot and, therefore, poop a lot. This equates to lots of feeding and cleaning. Most cephalopods, with the exception of the nautilus, naturally have short life spans ranging from half a year to a few years. As a result, culturing generations becomes necessary to continuously exhibit these animals and reduce the need for wild-caught animals.

What is it about cephalopods in general—and nautiluses in particular—that captures our imagination?
Cephalopods have a lot of unusual characteristics that make them seem like they come from another planet. They have many arms and tentacles. Some can change the color and shape of their skin to camouflage with their environment. And finally, the nautilus provides a great example of a "living fossil"—remaining unchanged for millions of years.

Which species of cephalopod do you most admire, and why?
The nautilus, of course! It looks different from other cephalopods, and its ability to maintain buoyancy using its shell is unique. But my other favorite cephalopods are the Hawaiian day octopus, flamboyant cuttlefish and the broadclub cuttlefish because of their flashy colors and ability to camouflage.